CHARACTERIZATION OF THE THIRD INTERCONDYLAR TUBERCLE OF PARSONS: AN ANATOMIC STUDY

Participants: E. Yian, L. Gallo, J. Kuhn, R. Hughes

Keywords: tibia, coordinate measuring machine, meniscus

Introduction

F. G. Parsons first described observations of a small bony prominence, the third intercondylar tubercle of Parsons (TITP), seen at the anteromedial tibial attachment of the anterior cruciate ligament on the outer margin of the internal articular facet. It has been reported in 3-45% of all persons. Various proposals have been formed to account for its existence ranging from soft tissue molding to pathologic traction as a result of knee instability. The overall goal of our study is to characterize and describe the TITP from anatomical dissections of human cadavers. Our hypothesis is that the TITP height correlates with the degree to which the anterior horn of the medial meniscus inserts anteriorly on the tibial plateau. In extreme circumstances the TITP could act as a bony replacement, remnant, or structural support of the anterior horn of the medial meniscus on the tibial plateau. This study will provide useful information toward the application of meniscal transplants.

Materials and Methods

Twenty-one human cadaver proximal tibia specimens were dissected with preservation of the menisci. Specimen age, gender, cause of death, and radiographs will be recorded. Each specimen will be cut approximately five inches distal to the tibial plateau and secured in a fixture using eight set screws. All measurements will be taken using the Coordinate Measuring Machine (CMM). Initial qualifications will be taken using the reference sphere and the fixture’s axis will be aligned with the workspace before any data is recorded. Three points will be recorded. To measure the insertion point of the meniscus, the anterior most point along the medial plateau and the inferior and anterior most point of the anterior horn will be determined using the ‘measurements’ option. The height of the TITP will be measured as an absolute distance from the plane constituting the base of the hump using the ‘3D distances’ option. All measurements are recorded according to specimen number.

Results

All specimens have been tested. A statistically significant correlation was found between TITP height and meniscal insertion location. A manuscript has been submitted to Arthroscopy.